Magnetoelectric ignition apparatus



Feb. 4, 1941. J. BoHLl MAGNETOELECTRIC IGNITION APPARATUS Fned May 11, 19.57 :s sheets-sheet IHHIIIIIIIIII 1N VENT OR.

Feb. 4; 1941. J. BOHLI 2,230,878

MAGNETOELECTRIG IGNITION APPARATUS Filed May 11, 1957 s sheets-sheet 2 Feb. 4, 1941. J. BoHLl MAGNETOELECTRIC IGNITION APPARATUS Filed May ll, 1957 3 Sheets-Sheet 3 l llll INVENTOR. ,n//akob 64M/ M f A ORNEY Patented Feb. 4, 1941 I UNITED STATES MAGNETDELECTRIC PATENT OFFICE IGNITION ArgrAaA'rUs Application May 11, 1937, Serial No. 142,061 In Germany and Switzerland May 27, 1936 '2 Claims.

The presentinvention relates to magnetoelectric ignition apparatus particularly for internal combustion engines.

For incorporating magnetoelectric ignition apparatus in internal combustion engines, it is desirable in various respects that the apparatus possess a generally symmetrical shape. There are ignition devices already known that fulfill this requirement. 'Ihe primary. and secondary windings which make up the ignition coil of such apparatus are arranged coaxial with the drive shaft, and the inductor is built so that the entire magnetic flux 'is led simultaneously through the coil. As a consequence of this arrangement, an extremely high difference of voltage exists between the layers at the moment-of rupture of the primary circuit, so that puncture of the insulation often results. The object of this invention is a' magnetoel'ectric ignition device for internal combustion ens gincs by which, in spite of its generally symmetrical form, this disadvantage is avoided. This ignition device is characterized in that its induction coils are distributed over several magnetic circuits; in which a ux is produced simultaneously by means of a pluralty of permanent` magnets. I

The drawings show several embodiments of the invention.

Fig. 1 is an axial section through a first embodiment; 7 v

Fig. 2 is a cross section on the line II--II in Fig. 1;

Fig. 3 isa section on the line III- III in Fig- 2;

Fig. 4 is atop view of the rotor;v

Fig. 5 is a section on the line V-V in Fig. 4;

Fig. 6 is a schematic representation of the magnetic flux circuits;

Fig '7 is a schematic representation of the electromagnetic system of a second'embodiment;

Fig. 8 is a schematic representation` of a third embodiment;

Fig. 9 is a section on the line IX-IX in Fig. 8;

Figs. 10 and l1 show a metallic shield covering a distributor head;

Fig. 12 is a schematic representation of an ignition device according tothe invention with two magnetoelectric systems working in parallel; and

Fig. 13 shows a schematic representation of a fth embodiment.

In the embodiment set forth in Fig. 1, the stator comprises two circular plates 3 and 3 of non-magnetic material, which are connected to cach other by six laminated soft iron bars 6, running parallel with a drive shaft 5. In the upper plate the bars 6, circularly arranged at regular intervals, extend to the bottom of a recess concentric with the shaft 5, filled between the bars with laminated soft iron pieces 4. In the lower plate the six bars `go through and are flush with the surface of the plate. The plates 3 and 3 are furthermore connected with bolts which are not shown. Each of the soft iron bars carries a primary winding 8 'and over it a secondary winding 9. These windings are connected in series with the primary and correspond` inglyA the secondary windings of the other soft iron bars. The combined primary windings and the combined secondary windings are likewise in series, and are connected in familiar fashion with a. breaker I0 mounted on plate 3 and with a high tension distributor II seated on the shaft 5. Furthermore, a condenser l lies parallel to the primary winding coaxial with the drive shaft, arranged on. a spool-like body of,insulation.

- The plates 3 and 3 have a coaxial bore provided .with a ball bearing in which the drive shaft 5 is journalled. The rotor also has a circular disc l of non-magnetic material. It carries a number of cylindrical permanent magnets I2 corresponding to the number of soft iron, bars 6 which are arranged at uniform intervals in a concentric circle of the diameter of the circle passing through the centers of the bars 6. The magnets I2 are magnetized laterally, that is their two poles lie on the two sides of an axial section passing through these magnets (see Fig. 4) The magnets I2 are connected with each other through a laminated soft ironring I3 which is pressed into a corresponding groove in the rotor and so arranged that like poles of two such magnets are turned toward each other. The magnetic flux of the described arrangement is the following (illustrated schematically in Fig. 6):

On account of the lateral arrangement of the magnet poles, the neutral position of the rotor will be obtained when one magnet I2 is exactly between two soft iron bars 6. The flux of two adjacent magnets flows then from the north poles which face each other through the laminated soft iron ring sections I3 which join them, unites inits middle, jumps the air gap I5 and traverses the whole length of the laminated soft iron bars r 6. At the end of the latter, one half of the flux goes to the left and the other half to the lright through the laminated iron ring 4 to thev next soft iron bars 6 which it traverses in opposite direction, jumps the air gap again and enters 'in the remaining bars.

the laminated ring I3 between the south poles of the magnets from which it originated, and the south poles of the neighboring magnets and returns to the south poles of the said original magnets. After rotation of a rotor around cnesixth of its circumference, the magnetic lines fiow in the bars 6 inthe opposite direction. The direction of the lines of force changes therefore six times in each revolution of the rotor.

By virtue of the special arrangement of the permanent magnets in the rotor, it is also possible to produce an odd number of sparks for each revolution of the rotor. For example, for five sparks per revolution, five soft iron bars 6- are needed. 'Iherotor is adapted for the reception of ve permanent magnets arranged at equal intervals, but only four are used. In place of the fth magnet, a non-magnetic cylinder I4 with the same dimensions as the magnets I2 is substituted. Such an arrangement is shown schematically in Fig. 7. The magnetic lines run in analogous manner to the above description With the difference that now the laminated soft iron ring sections I3 on both sides of the non-magnetic cylinder I4 do not have any flux in onehalf thereof. Upon rotation of the rotor, the direction of now of lines of force reverses at each fifth of a revolution of the shaft whereby each two adjacent soft iron bars 6 in rotation carry only one-half of the ux of the other bars. Consequently, in the windings of these only halfenergized bars, a smaller current is induced than Since, however, the coils of each bar are connected in series, and the smaller induction' in two of these coils is constant during the whole revolution of the rotor, there is obtained, in spite of the apparent asym-` metry of the arrangement, a/ constant high tension value for all inductive positions of the rotor.

The breaker is in that case arranged for ive breaks per revolution of the rotor. In like manner, it is, of course, possible to obtain any desired Y uneven number of breaks, and accordingly of sparks, per revolution of the rotor. By this arrangement, the usual gearing between the engine cam shaft and ignition apparatus may be eliminated.

The arrangement just described and illustrated in Fig. 7 has, besides the simple arrangement of the apparatus for odd numbers of sparks, the further advantage that the polarity of the generated sparks changes after each revolution of the rotor so that .a uniform burning away of the electrodes takes place.

The rotor and stator are enclosed in a cylindrical light metal housing I6 which is provided on the inside with shoulders II and I8 forming' bearings for the stator plates 3 and 3. To secure the stator against .axial shift, a recess I9 is provided in the shoulder `I8 in which Va spring 20 formed as a split ring is iitted. The housing I B is closed by a high tension distributor cap 2| made of insulating material. The lower part of the housing is formed as a bearing for the rotor shaft. The stator might be merely jounialled on the rotor shaft instead of in the housing, and

simply secured by an anchoring device against` bodiment, the diameter only is considerably increased, whereas its height can be notably reduced, which is desirable in certain cases due to construction diiliculties. The remaining construction of the device is the same as in the exemplary embodiment of Fig. 1.

The ignition device can also be built in the manner shown in Figs. 8 and 9. The stator is here enlarged in comparison to the rotor. Its upper part is the same as in the embodiment of Fig. 1. In the lower part, the soft iron bars E are extended over the whole length of the rotor, and are formed below as pole shoes 6". The lower non-magnetic plate `3" is provided with corresponding cut-outs to receive these pole shoes. The rotor consists of a ring of laminated soft iron pole shoes 22 held together by non-magnetic discs 23, in between which poles the laterally magnetized permanent magnets I2 are pressed. As can be seen from the drawings without further elucidation, the magnetic circuit and the mode of operation of the device are exactly the same as in the exemplary embodiment of Figs. 1 to 6.

To obtain greater reliability i n the ignition of aircraft motors, this ignition device could be built so that on one and the same drive shaft two magnetoelectric systems are mounted, which operate on the same cylinder in parallel in such manner that in case of failure of one system, the other would maintain the operation of the engine. Such an arrangement is shown schematically in Fig. 12. `Numerals 24 and 24' are the two rotors and 25 and 25' the twostators. It would also be possible with corresponding dimensions of magnets to provide only one rotor which energized both stators.

Another embodiment which produces an especially powerful spark is schematically shown in Fig. 13. In this construction a rotor I and I' of the kind shown in Fig. 5 is provided on drive shaft 5 at each end of the stator. Both magnetic rotors have the same number of magnets and .are so arranged on the shaft 5 that in the direction of the axis a north pole of the rotor I (formed by the soft iron piece of the ring I3 lying between two north poles) stands opposite a south pole of the rotor l. The soft iron cores B of the stator go through the non-magnetic plates 3 and 3 at both ends. The lines of force now flow from each two adjacent north poles of one rotor through the piece of the soft iron ring I3 which lies between them, then traverses the air gap, the soft iron cores 6, the second air gap, enters the piece of the soft iron ring I3 of the other rotor, and into the adjacent south poles.

It is self-understood that in the embodiment shown and described, the number of the permanent magnets and accordingly the number of the soft iron cores 6 may be chosen differently as desired. Thus the ignition device according to the invention may very well consist of only .two permanent magnets and .two soft iron bars 6. The apparatusfcould also be so built that the plates with the permanent magnets remain stationary, and the system of soft iron bars with the windings rotates.

In order to shield the ignition device against the radiation of electromagnetic waves, a twopart metal hood 29 illustrated in Figs. 10 and l1 is provided which covers the distributor cap ZI. The matched surfaces of the two halves are provided with an offset 26 running over their entire length. 'Ihe hood overlaps with its lower inwardly bent edge 21 a band 28 of the housing I6. As the latter is likewise composed oi metal, the magnetoelectric system contained therein is protected by a completely enclosed metallic shield from the radiation of interfering radio waves.

The ignition device according to the invention oilers various essential advantages in comparison with apparatus hitherto known for similar purposes. Thus, for instance, in consequence of .the axial Vpassage of the flux lfrom the inductive to the induced part, a considerably smaller diameter of the device is obtained than is the case in apparatus with radial nux paths. Since .the stator, together with the ignition coil and the breaker, is rotatable around the drive shaft, the ignition timing can be readily adjusted with .the aid of very simple means, for example by turning of the housing when the stator is mounted in it, or lby a special device if the stator is only mounted on the rotor shaft. Thanks to the sub-division and connection in series of the ignition coil windings, uneven remanence of the separate magnets, or unlike air gaps have no great influence on the shape of the curve of the generated cur rent. v

By the use of laterally polarized magnets which produce a relatively large magnetically eilective cross section, a very compact construction ofthe device is secured. y

What is claimed is:

1. In a magneto, a magnetic rotor and a stator arranged end to end, said stator having an odd number of equally spaced pole pieces, the latter being circumferentially arranged, and ilux conducting means magnetically connecting said pole pieces to each other, and said rotor including an even number of spaced bar magnets with like poles adjacent to each other and means for magnetically connecting like poles of said magnets,

all .but one of 4the spaces between saidmagnets.

being substantially equal to the spaces between said pole pieces.

2. In apparatus of the class described, a casing, a non-magnetic member having an annular groove mounted in said casing, a plurality of circumferentially spaced ilux yconducting bars extending into said groove, flux conducting means for magnetically connecting the ends of said bars in said groove, primary and secondary coils surrounding each of said bars, non-magnetic means for holding the other ends of said bars in spaced relation, and a rotor adjacent said last named ends of said bars including a disc-like member having an annular groove therein, a series of bar magnets spaced in said last-named groove with like poles adjacent and ux conducting pole pieces connecting like poles of said magnets in said last-named groove.

JAKOB BOHLI. 

